Doe claims to represent the sin of "Envy"; he was jealous of Mills' normal life, and killed Tracy after failing to "play husband" with her.

But the viewers don't have first hand account of whether the murder actually took place.

Is it possible that John Doe (played by Kevin Spacey) didn't actually kill his wife? If he really did, how can the viewer be sure of the murder other than the subliminal appearance of Tracy Mill's face when the box was opened and John Doe's account to David Mills?

So apart from the fact that John Doe had murdered 5 other people in a grisly and symbolic manner, and the brief glimpse of the head, David Mills murderous reaction, and zero evidence to the contrary. Wow, you could doubt pretty much any plot point in any movie on this basis.
– iandotkelly♦Jun 28 '12 at 13:20

Well you can happily delete this question if you think it is absurd.
– jokerdinoJun 28 '12 at 13:23

Well I tend to only close questions that are clearly off-topic. If people think its absurd or good can vote on it.
– iandotkelly♦Jun 28 '12 at 13:26

1

mill's wife dead and what character she supposed to be?
– user4076Feb 7 '13 at 15:54

Why else would David Mills be going so crazy after opening the box? The box was bloody, that was Cheryl Mills' face in there. Doe had killed his wife. It was to cause his final desire to push David Mills to commit the deadly sin of wrath, the seventh deadly sin.
– MissouriSpartanJun 12 '18 at 21:32

Note, as far as I recall the viewer never gets a glimpse inside the box, so, in one sense, the movie deliberately withholds evidence from the viewer. This might leave you doubting that Jon Doe had murdered Mills' wife.

But the context of the scene does not. We know the characters of the individuals: John Doe is clearly capable and motivated to commit the murder and, to make his epic point, he has to commit an act capable of inciting Mills to the sin of Wrath; Somerset has a deep understanding of human motivation and the specific pattern of Doe's crimes; Mills is in love with his wife and is not such a poorly controlled cop that he would react with vengeful wrath to many insults.

The scene plays out with Somerset opening the box. Somerset's reaction to seeing the contents suggests he knows immediately what Mills will do. He attempts to stop Mills obvious action by persuading him to disarm before looking in the box. What other possible content in the box could cause this reaction? Mills then looks and reacts with vengeance. What else could have persuaded him to do so? Mills has seen other atrocities committed by Doe and did not react this way.

The only possibility here is that Doe has done what he claimed and the box contains Mills' wife's head. The fact it is not shown explicitly actually makes the climax more tense. You don't need to see everything to know what has happened (subtlety is good and treats audiences as intelligent people).

Thank you for your interest in this question.
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